SHENZHEN, China—Revenue of China’s Huawei Technologies Co. Ltd. plummeted 38 percent in the third quarter compared to the same period a year earlier, with U.S. sanctions having hobbled its smartphone business and new potential growth areas still in their infancy. The Chinese telecoms giant posted revenue of 455.8 billion yuan ($71.32 billion) for the first three quarters on Friday, down by almost a third on the same period a year earlier, with a profit margin of 10.2 percent. Revenue for the third quarter alone came to 135.4 billion yuan, based on Reuters calculations. Performance was “in line with forecast”, said rotating Chairman Guo Ping. Former U.S. President Donald Trump put Huawei on an export blacklist in 2019 and barred it from accessing critical U.S.-origin technology, impeding its ability to design its own chips and source components from outside vendors. The restrictions have badly hurt Huawei’s handset business, with rotating Chairman …